Microtomes utilize an extremely sharp blade to cut tissue specimens into thin slices for microscopic histological examination. Histological cassettes are often used to prepare tissue specimens for microscopic examination and to hold such tissue specimens during the slicing process.
During preparation of a tissue specimen, the tissue specimen is often placed in an interior compartment of a histological cassette and immersed in various fluids such as ethanol, xylene, formaldehyde, and water. After treatment of the tissue specimen is complete and prior to the slicing operation, the cassette and tissue sample are typically immersed in molten paraffin. The lid of the cassette is thereafter opened and tissue sample is removed from the cassette prior to the complete solidification of the paraffin. Following this step, the tissue sample is placed in a cavity formed in an embedding mold. The cassette is then placed above the tissue sample in the embedding mold and additional paraffin is used to secure the tissue sample to the exterior of the cassette adjacent the bottom surface of the cassette.
Microtomes are often fitted with cassette holding assemblies that are configured and adapted to securely hold a cassette and to pass very close to the blade of the microtome in a reciprocating manner. Additionally, the cassette holding assembly is typically able to move in very small and precise increments toward and away from the microtome blade in a direction perpendicular to the direction of reciprocation. Generally, a cassette is held by the cassette holding assembly in an orientation such that a tissue specimen, which is adhered to the cassette via solidified paraffin, engages the microtome blade with each reciprocating pass of the cassette holding assembly, thereby creating thin slices of the tissue specimens that are suitable for microscopic histological examination.